Lenses of the aforementioned type are generally known and are widely used for imaging. However, frequently partial amounts of light from a luminous flux passing through the lens need to be coupled out during imaging, for example, to measure the light intensity of the luminous flux in imaging devices. Until now, partially transparent mirror were used for this purpose, which are arranged along the luminous flux before or after the lens. The use of the semi-transparent mirrors, however, requires additional space, which is limited especially for compact imaging devices.